CrossRoads:
The On/Off times are kind of slow, probably ok as you will not be switching on & off with great frequency.
The On-Resistances are kind of high, which may impact your frequency response.
Actually, slow relay response times might be a problem. In most cases, the user will want to change from one effects loop (say, a clean sound) to another effects loop (say, a distorted sound) in time with the music. I can see a delay causing problems in two areas - firstly, if it creates silence while switching, and secondly that it might make the change out-of-time with the music.
I've come across something called a "high speed relay" http://australia.rs-online.com/web/p/pcb-solid-state-relays-ssr/1718667/?cm_mmc=AU-PPC-0411-_-google-_-1_EEM_Generic_Dynamic-_-_inurl:relays#inurl:australia.rs-online.com_Broad.
Would that be more suitable?